Faced with the scarcity of Samuel Beckett's theoretical writings, one has no choice but to look for them throughout his correspondence. In this prospect, the publication of Samuel Beckett's letters offers a great opportunity to find the fragments of a treaty on aesthetics Samuel Beckett never wrote. In many letters Samuel Beckett analyzes and ponders over his own works as well as those by other writers, painters and musicians. This paper analyzes what can be considered as 'aesthetics in progress,' aiming at understanding the categories and the concepts particularly relevant to study Samuel Beckett's works. The Letters of Samuels Beck 1929-1940 provides an inner view upon Beckett's creative method and therefore offers an interesting counter point to Beckett's silence when it comes to comment his own works.